Brian Nuttal, a rather famous breeder and worker of Patterdale Terriers, was asked by the editors of the Fell and Moorland Working Terrier Club's Annual Yearbook (Volume XXX): "Have you any strong dislikes about Terrier sport or its participants?"
"One strong dislike I have is the type of Terriermen who kills everything they dig or bolt, cubs or adults, and sell for fox pelts. They are usually the first to complain when quarry is scarce. I know these people are in the minority, but they give a bad name to all. Most of the foxes I dig or bolt are released unharmed, unless they have been doing damage to poultry, pheasants or the like."
Mr. Nuttal's thoughtful answer indicates someone who has a solid understanding not only of the dynamics of fox population densities and diet, but also someone who understands that terrierwork can easily be harmed by the ham-fisted, the ill-advised and the poorly taught.
For more thoughts on ethical terrierwork, see >> here